A novel method for quantitative height measurement based on an astigmatic optical profilometer

Astigmatic detection systems have been used in hybrid systems to produce both contact and noncontact profilometers, which provide advantageous features such as low cost, small laser spot, high bandwidth, and compact size. However, current astigmatic optical profilometers cannot provide quantitative height measurement on a surface consisting of complex materials. In this paper, a novel method called z-axis modulation is proposed to overcome this limitation. A homemade astigmatic optical profilometer was developed, and an analytical process for height calculation was also developed. As demonstrated by the experimental results, z-axis modulation can provide accurate height measurement. Furthermore, optical properties such as reflectivity can also be measured. (technical note)